The present invention relates to a flexible optical material in the shape of tape or floppy disk as an information recording medium and more particularly to a flexible optical material comprising an optically isotropic laminate and a recording layer disposed on at least one side of said laminate.
The optical tape or floppy disk for recording information as a function of light energy input is in the development stage today and has been considered to be a useful means of information recording in view of the remarkably high recording density it provides as compared with the magnetic tape.
Several patent applications are already pending in the field of the optical tape. For example, Japanese Unexamined Patent Application No. KOKAI 62-78746 (1987) discloses an optical tape comprising a flexible tape support and an optical recording medium composed of a metal or alloy of variable spectral reflectance. The flexible tape support is described to include plastic bases such as those of polyethylene terephthalate, polyimide, polyvinyl chloride, polycarbonate, etc. and, in the examples shown, a polyimide tape is employed.
Such flexible bases for the optical tape are required to satisfy the following requirements: transparency, a minimum of birefringence (optical isotropy), a sufficient degree of heat resistance to withstand dimensional change or curling under the temperature conditions prevailing during production or use, resistance to the solvent used for coating with the recording medium, resistance to moisture penetration (water vapor impermeability), satisfactory mechanical strength and hardness to withstand deformation, low thermal conductivity, flexibility, and gas impermeability (gas barrier property).
However, the flexible tape bases described in Japanese Unexamined Patent Application No. KOKAI 62-78746 (1987) are only able to meet some of the above requirements and need improvement for practical usefulness.
It is an object of the invention to provide a flexible optical material in the shape of tape or floppy disk including a specified optically isotropic laminate.
Other objects and advantages of the invention will become apparent from the detailed description given hereunder.